Transmission cables are intended to operate safely and effectively over lifespans exceeding twenty years. However, because of anomalies in the transmission cable due to manufacturing defects, installation errors, localized imperfections, such as insulation breakdown, transmission cables often suffer premature breakdown. Should this occur during a critical period the repercussions in terms of financial losses and customer inconveniences can be quite severe. Therefore, with the ever-increasing number of transmission cables being utilized throughout the world, it is desirable that anomalies such as faults, discharges, cable damage, and splices of transmission cables be located without the necessity of physical tracing and inspection.
A Time Domain Reflectometer (TDR) is one apparatus that can be used to analyze a cable for anomalies, and more specifically, to analyze the cable for changes in cable impedance in order to locate such anomalies. A typical TDR transmits a pulse of electrical energy onto a cable that includes two conductors separated by a dielectric material. When the pulse encounters a change in the impedance of the cable, part of the pulse's energy is reflected back toward the TDR. The amplitude and polarity of this reflection is proportional to the change in impedance. Such reflections are usually displayed in graphical form on the screen of a typical TDR whereby a technician can interpret the results and locate specific cable anomalies. In particular, the time of propagation of the pulse as well as the pulse shape can be used to identify and locate the anomaly along the transmission cable.